This invention relates to an efficient low cost traveling wave tube having a high power capability.
Traveling wave tubes are used to amplify signals in microwave systems including electronic countermeasure systems. Some applications require that the traveling wave tube be expendable. Accordingly, it is desirable to provide a reliable low cost traveling wave tube that is capable of efficiently amplifying microwave signals over a wide bandwidth and at a reasonably high power level.
Efficient traveling wave tubes having a wide bandwidth and high power capability are known to the prior art. These tubes are of complex construction and expensive since they must adequately dissipate heat during high power operation and at the same time provide a high coupling impedance into and out of the tube. These tubes usually include a helix formed from a wire having a square or rectangular cross section disposed within a vacuum formed within a metal barrel heat sink. The helix is supported by three or more dielectric rods equally spaced about the helix and in contact with both the helix and the metal barrel heat sink. The helix is secured to the rods at each point where the helix comes into contact therewith to establish a thermal conductive path from the helix to the metal barrel heat sink for heat dissipation. The power capacity of these tubes is limited by the capability of the structure to dissipate heat through the limited point contacts between the helix and the support rods.
Increasing the width of the dielectric rods to provide greater surface area for heat transfer from the helix to the dielectric rod has not provided an acceptable solution because the wider rods increase the dielectric loading which decreases the coupling impedance into and out of the tube, thereby decreasing both gain and bandwidth.
The traveling wave tubes known to the prior art are of a configuration that provides for sufficient heat conduction through the dielectric supports while maintaining a relatively low dielectric loading. To accomplish this, expensive and complex tube configurations are required.